Egg rolls, a well-known finger food, should hold together while you bite off pieces and dip the roll in sauce. Properly sealing an egg roll also makes it more visually appealing and "user friendly." The trouble with an improperly sealed egg roll begins well before it reaches your plate, because improper sealing prevents it from holding together during the frying process.
Drain the egg roll filling before laying it on the wrapper. Excess moisture makes an egg roll soggy and can make it fall apart. Use as much filling as you can, without overstuffing the egg roll. Overfilling makes the roll difficult to seal.
Lay an egg roll wrapper on a flat, clean surface, orienting it on a diagonal. Lay a couple of tablespoons of filling across the center of the diagonal, starting about an inch and a half from one corner and ending about an inch and a half from the opposite corner.
Add one part cornstarch and one part water to a small bowl. The cornstarch and water mix makes a sealing liquid. Dip your finger in the mixture and run a small bead along the two adjacent sides at the top half of the egg roll wrapper. Cover a strip of the wrapper about 1/3-inch wide. Use enough of the cornstarch mixture to fully coat the strip of wrapper, but avoid letting liquid accumulate on it, which makes the wrapper soggy.
Roll the egg roll by folding the bottom flap up to cover the filling and tucking the side flaps over to make an envelope. Continue rolling from the bottom to the top, and seal the egg roll as tightly as you can without squeezing out the filling. Once the egg roll is fully rolled, press the sealed edges lightly so that none of the fillings leak out.